The primary objective of this clinical research trial is to determine the safety, tolerability, and compatibility of ascending doses of harkoseride in patients with partial seizures who are on a stable, but less than fully effective antiepileptic drug (AED) regimen. Cecondary objectives are to assess whether harkoseride doses ranging from 200 mg/day to 600 mg/day can cause dose-limiting adverse events, and whether harkoseride has any effect on the steady-state plasma levels of concomitant AED medication. Other objectives were to assess the acute and steady-state plasma concentrations of harkoseride when given at doses ranging from 100 mg BID to 300 mg BID, as well as the assessment of the efficacy of harkoseride when given as adjunctive therapy. This initial Phase II trial is a multicenter, open label assessment of the safety, tolerability, compatibility, efficacy, and pharmacokinetids of harkoseride as add-on therapy for patients with partial seizures. Primary treatment with fixed doses of one or two approved antiepileptic drugs was supplemented with weekly-ascending doses of harkoseride over a 3-week period. Clinical and pharmacokinetic compatibility of the various drug combinations will be studies. The initial dose of investigational drug (Study Day 1) and those doses administered on Study Day 8 and 15 (the days of potential dosage increase of harkoseride) were given and evaluated under in-patient conditions. The remainder of the study will be coducted on an out-patient basis.